The present invention concerns a medicament containing non-staling chewing gum and particularly chewing gum useful for delivery of measured doses of antacids.
Attempts have been made in the past to utilize gum as a carrier for medicaments. Chewing gum is relatively inexpensive, its manufacturing processes are well known and gum can be flavored to minimize the negative taste sensations associated with certain medicaments.
U.S. Pat. No. 4,265,877 issued to Louis T. Tenta discloses a chewing gum base with a mixture of sodium fluoride and calcium carbonate in the form of oyster shell distributed within the base. This invention is directed toward the use of the combination to introduce fluoride as a suitable medicament. Calcium carbonate is routinely used as a filler for chewing gum, and calcium carbonate as well as other water insoluble salts remain within the gum base during mastication.
U.S. Pat. No. 3,011,949 to A. G. Billotti discloses the concept of spray drying otherwise insoluble particulate medicaments, such as calcium phosphate, antacids, etc., with sugar and mixing with sugar in a conventional gum formulation. According to this patent, mastication liberates a large percentage of the medicament as well as the sugar that was spray dried with it. Subsequent experiments have, however, failed to duplicate the high degree of insoluble medicament liberation set forth in this patent. Apparently, the degree of liberation is highly dependent upon the particular spray drying process used.
U.S. Pat. No. 4,208,432 to Ker-Tchi Noborio discloses the use of either alpha lactose, beta lactose or calcium carbonate along with certain saturated fatty acid monoglycerides as a powdery releasing agent.
Frank Witzell et al in U.S. Pat. No. 4,238,475 discloses introducing magnesium hydroxide or calcium carbonate or the like in chewing gum by including a water soluble phase formed of an aqueous softener with the softener being coated by a water soluble coating agent. This sequence of steps is part of an otherwise conventional process for manufacture of chewing gum.
U.S. patent application Ser. No. 644,734 filed in the name of S. Rao Cherukuri et al. Aug. 27, 1984, now allowed, discloses a non-staling low moisture chewing gum with substantial organoleptic and stability advantages as well as process advantages when compared to conventional chewing gum. The chewing gum composition set forth in the Cherukuri et al. application has a moisture content of up to 1.0% by weight of the final composition and comprises a gum base which softens in a temperature range of about 40.degree. to about 60.degree. C., a flavoring agent, softener such as lecithin and the like and a sweetening agent. The ingredients contain only residual moisture and are added to the composition without the use of aqueous solutions.
It is essential that the final chewing gum composition must have an equilibrium relative humidity value lower than the ambient relative humidity. Equilibrium relative humidity is a means for identifying the susceptibility of a composition to gain or lose moisture which in turn relates to the tendency for the gum to remain moisture stable, i.e., not to dry out or become stale. When the gum base disclosed in the Cherukuri et al. application neither picks up nor loses moisture it is in the state of equilibrium with the environment. The equilibrium relative humidity depends on the ratio of free moisture to bound moisture in a product as well as the temperature of the product and environment. The amount and rate at which a chewing gum loses or gains moisture depends upon the differential between the product's equilibrium relative humidity and ambient relative humidity. Since the equilibrium relative humidity of the gum is substantially below that of the environment in most geographic regions, the gum disclosed in the Cherukuri et al. application will not lose moisture. The equilibrium relative humidity of the Cherukuri et al. gum range between 15 and 30% and generally between 21 and 25% at about 23.degree. C. to retain this differential.
The factors, according to the Cherukuri et al. application, which provide the extended shelf life associated with the low moisture gum are first, omitting moisture and moisture containing ingredients in the chewing gum formulations; second, maintaining the equilibrium relative humidity of the chewing gum composition at a lower level than the ambient relative humidity; and third, using a gum base which softens between the temperature of about 40.degree. C. and 60.degree. C. The last restriction, of course, limits the use of the elastomers to produce this gum.
Another distinction claimed for this particular gum is that during processing the gum base is softened rather than melted. Softened is defined as heating to a semiviscous state or when the viscosity is relatively high and the base has better film forming and stretching characteristics than bases which are melted. The preferred softening temperature is between 50.degree. and 55.degree..
The amount of base varies between 5 and 55% by weight of the final gum compositions with 20 to 35% by weight being preferred.
The Cherukuri et al. gum can also utilize plasticizers or softeners such as lecithin and the like which may be incorporated in the gum base and these additional materials may be present in amounts up to about 30% by weight but preferably from 3 to about 7% by weight of the final gum base composition. Mixtures of these ingredients can also be used.